PCA9538 查看數據表（PDF） - NXP Semiconductors.

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PCA9538

8-bit I2C-bus and SMBus low power I/O port with interrupt and reset

NXP Semiconductors. 

NXP Semiconductors

PCA9538

8-bit I2C-bus and SMBus low power I/O port with interrupt and reset

7.1 Minimizing IDD when the I/Os are used to control LEDs

When the I/Os are used to control LEDs, they are normally connected to VDD through a

resistor as shown in Figure 11. Since the LED acts as a diode, when the LED is off the

I/O VI is about 1.2 V less than VDD. The supply current, IDD, increases as VI becomes

lower than VDD.

Designs needing to minimize current consumption, such as battery power applications,

should consider maintaining the I/O pins greater than or equal to VDD when the LED is off.

Figure 12 shows a high value resistor in parallel with the LED. Figure 13 shows VDD less

than the LED supply voltage by at least 1.2 V. Both of these methods maintain the I/O VI

at or above VDD and prevents additional supply current consumption when the LED is off.

VDD

3.3 V

5V

VDD

IOn

LED

100 kΩ

VDD

LED

IOn

002aac660

002aac661

Fig 12. High value resistor in parallel with Fig 13. Device supplied by a lower voltage

the LED

PCA9538_5

Product data sheet

Rev. 05 — 28 May 2009

© NXP B.V. 2009. All rights reserved.

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